Researchers at Trinity College Dublin and the University of Manchester have made great strides in improving how we recycle polyester terephthalate, the most common type of plastic found in drinks bottles and food containers. The research, led by Dr Cristina Trujillo and Professor Stephen Connon, was published in the journal RSC Sustainability. The team’s work focuses on using environmentally friendly choline-based liquid salts for a process called glycolysis, which breaks down plastics into their core components so they can be reused.
Plastic waste is a growing problem, and polyethylene triacetate, a key material in many everyday products, is a major contributor. Unfortunately, efficient recycling cannot be achieved by standard mechanical methods due to contamination or repeated use. When plastic is recycled this way, it often results in a lower quality product. Glycolysis, on the other hand, offers a way to recycle plastic back into high-quality material, almost like new. “There is growing interest in the use of choline-based liquid salt catalysts to recycle polyterephthalate via glycolysis,” Dr. Trujillo emphasized. The goal is to find more efficient and environmentally safe ways to do it. to this point.
Their research involved computer simulations and laboratory experiments to better understand how many key parts of liquid salt help break down plastic. Previous research has shown that choline plays an important role in chemical reactions, helping to stabilize certain parts of the process. However, this new study shows that other factors, such as the solvent ethylene glycol, are actually more important than previously thought. “Our findings suggest that while choline-based liquid salts have potential as catalysts for chemical recycling of plastics, the role of the choline cation itself may be overstated,” explains Professor Connor.
Through various tests, the researchers compared different liquid salt catalysts, including new versions that did not include choline. Some of these alternative catalysts work better, using less material while achieving higher effectiveness. One particular type of efficiency stands out using phosphorus-based catalysts. The data show that these alternative catalysts significantly outperform choline-based catalysts. The findings are crucial because they suggest there are more efficient and sustainable ways to recycle plastic.
The appeal of choline is the fact that it is biodegradable, meaning it breaks down naturally and is less harmful to the environment. However, the nearly equal performance of alternative catalysts suggests that choline’s real advantage may be more about its environmental benefits than its ability to help in the recycling process. Dr. Cristina Trujillo noted: “This opens the door for future research to explore choline-free biodegradable catalysts that provide a more efficient recycling process while still being environmentally friendly. “
The research has wider implications than just recycling plastic bottles. It highlights the need to revisit commonly accepted ideas in chemistry, especially when developing greener technologies. The team plans to continue studying how different solvents and catalysts affect the recycling process to make it more environmentally friendly. These continued efforts could lead to better, more sustainable ways of managing plastic waste and help achieve global environmental goals.
Overall, the research represents an important step in finding greener recycling methods. It challenges the idea that choline is essential for the recycling process, suggesting that other liquid salt catalysts may be better. But the continued development of these catalysts, whether based on choline or not, holds great promise in solving the growing plastic waste problem.
Journal reference
Bura D., Pedrini L., Trujillo C., Connon SJ “Choline-based ionic liquid catalysts for polyterephthalate glycolysis: understanding the role of solvent and redistribution of cationic contributions.” RSC Sustainability Sex, 2023. DOI: https://doi.org/10.1039/d3su00336a
About the author
Dr. Cristina Trujillo Obtained her PhD in Theoretical and Computational Chemistry, University of Madrid (Spain) in 2008. During 2008-2016, she held several postdoctoral positions in Spain (CSIC), Prague (Academy of Sciences) and Ireland (Trinity College, Dublin). From 2016 to 2018, she worked as a researcher at TCD. Afterwards, she worked as an Assistant Lecturer at Tu-Dublin in the School of Chemistry and Pharmacy. She was awarded a very competitive SFI Starting Researcher Research Grant (SIRG, 2018) and a L’Oreal-Unesco Women in Science Fellowship in the UK – with great gratitude (2019). She served as an independent researcher from 2019 to 2022, leading her own research group at TCD. Currently, she is a lecturer in computational and theoretical chemistry at the University of Manchester.
She has expertise in highly fundamental topics in computational organic chemistry such as asymmetric catalysis, computationally led catalytic design, reaction mechanisms and non-covalent interactions. Her research interests focus on asymmetric catalytic fields, with a particular focus on the application of computational techniques in the design of organocatalysts, as well as the prediction and control of catalytic processes, with direct implications for the development of products with diverse applications.
Diana Bura is a third-year PhD student under the supervision of Dr. Cristina Trujillo at the Trinity School of Biomedical Sciences, Trinity College, Ireland. Her research journey began in the final year of her undergraduate studies at Trinity College Dublin, where she conducted theoretical studies on asymmetric conjugated catalysts of N-cysts within the Trujillo group. Currently, her PhD focuses on using density functional theory (DFT) to perform mechanistic studies in various areas of chemistry, including PET liberation, organocatalysis and drill catalysis. Her main research interest lies in the use of computational tools to improve the efficiency and sustainability of chemical research.
Lorenzo Pedrini Completed his Master’s degree in Medicinal Chemistry Technology from the University of Genoa, Italy, focusing his final project on the synthesis of imidazole-pyrazole derivatives, under the supervision of Professor Chiara Brullo. He later moved to Dublin and is currently completing his PhD. Under the supervision of Professor Stephen Connor of the Trinity School of Biomedical Sciences, Trinity College, Ireland. His work focuses on the development of novel biodegradable ionic catalysts for use in plastic recycling. He has experience in PET, organic synthesis, ion-utilization, depolymerization of ionic liquids and spectroscopic techniques.
